# Frequently Asked Questions

#### I've got a small ceramic disk capacitor, how can I tell it's value?

The first row will have a number like 33J, 104Z or 223Z, where first two digits denote significant figures; the last digit denotes the multiplier of 10 in pF. The letter denotes the tolerance, for which you should check the product data sheet. If there is a second row this will be the Manufacturer's Identification.
Examples:
33J = 33 x 100 pF = 33pF
104Z = 10 x 104 pF = 0.1μF
223Z = 22 x 103 pF = 22nF

#### What are the colour bands on a resistor?

Many resistors have 4 bands:
• The first band gives the first digit.
• The second band gives the second digit.
• The third band indicates the multiplier (number of zeros).
• The fourth band shows the tolerance of the resistor value
• Silver ±10%, Gold ±5%, Red ±2%, Brown ±1%
• Green ±0.5%, Blue ±0.25%, Violet ±0.1%, Grey ±0.05%

It's also common to find 5 Band resistors that will have 3 digits before the multiplier and tolerance, whereas a 6th Band show a temperature co-efficient.

eg. Brown Green Red Gold = 15 x 102 = 1500Ω also written 1K5

When we write 1K5 the K in the middle means thousand and replaces a decimal point that might be missed. Similarly we can use R and M for other factors, where 2R2 would be 2.2Ω and 5M6 would be 5.6MΩ or 5.6 x 106.
Colour
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
Number
0
1
2
3
4
5
6
7
8
9

#### How do compare different torque units?

There are a variety of units used, most common is Nm (Newton meters) but with small values you might see Nmm (Newton millimetres). This is relatively straight forward as there is a factor of 1000 between the two (1m = 1000mm), unfortunately other measures are also common but all are based on distance x force so conversions are not difficult.
in.oz
lb.ft
kg.cm
g.cm
N.m
in.oz
1
0.00521
0.072
72
0.00706
lb.ft
192
1
13.8
13800
1.36
kg.cm
13.9
0.0723
1
1000
0.0981
g.cm
0.0139
0.0000723
0.001
1
0.0000981
Nm
142
0.738
10.2
10200
1
In the case of in.oz (inch ounce) or kg.cm (kilogram centimetre) they are often depicted at in.ozf or kgf.cm to show a measure of force rather than mass.

#### What about other Frequently Asked Questions?

John Piccirillo's Robotics miniFAQ for Beginners can be found here as a PDF, updated Aug 2006.
The Robot Competition FAQ can be found here, and contains contains brief summaries of regular robot competitions around the world.

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